The invention relates to a radiodiagnostic apparatus with an X-ray tube, a diaphragm which is semitransparent in at least one region and which clears a slit of variable width to let radiation pass, with an x-ray image intensifier and a television camera coupled thereto for the generation of video signals, the camera being connected with a monitor for the reproduction of the video signals.
German Offenlegungsschrift No. 1,800,879 discloses a primary ray diaphragm for x-ray examination apparatus. Here, a semitransparent diaphragm consisting of two diaphragm plates attenuates the lateral radiations in the x-ray beam. Otherwise, particularly in the case of extremities, the unattenuated beam would directly strike the x-ray image intensifier input screen. This would produce bright areas which impair the perception of details in the actual viewing area. By the use of the semitransparent diaphragm plates these overradiated (or "bloomed") lateral areas are attenuated, so that the visibility in the area of interest is increased, although high-contrast objects (for example, surgical instruments brought in from the side) are still clearly visible. To properly orient the test object with respect to the radiodiagnostic apparatus, the diaphragm plates are rotatable on a diaphragm disk. For manual adjustment of the width of the non-attenuated ray path, the two diaphragm plates can be moved toward each other, until (in the ideal case) overradiated areas have disappeared. In the normal case of non-rectilinear contours, contour adaptation cannot be achieved with the rectilinear end faces of the diaphragm plates. Either a large portion of the object to be examined is attenuated as well, or else large parts of the television picture are still overradiated, so that the visibility of details continues to be reduced.
From German Offenlegungsschrift No. 29 05 202 a viewer ("light viewing box") is further known, where for the observation of transparent, rectangular pictures the image support can be darkened by a plurality of parallel and narrow cover strips. By placing pictures on the edge of the viewer, their size is picked up automatically. Subsequently only those strips which cover the picture are moved by a motor until the film is exposed also at its lower edge. Several films can be exposed simultaneously only if they are of the same vertical size. Adaptation to irregular contours is impossible by using the blades of this viewer.
One object of the invention is to provide, for a radiodiagnostic apparatus of the initially mentioned kind, a semi-transparent diaphragm which adapts itself as exactly as possible to the contours of the object to be examined, so that only small areas of the object being examined, or none at all, are covered up, or only small areas in the vicinity of the object are uncovered.